Method of regenerating platinum contact substances.



.UNITED STATES PATENT OFFICE.

OONS TANTIN KRAUSS AND RUDOLPH MI ILLER VON BERNEOK, OF I-IOCHST- ON-THE-MAIN, GERMANY, ASSIGNORS TO FARBWERKE, VORMALS MEIS- TER, LUCIUS & BRIINING, OF HOOHST-ON-THE-MAIN, GERMANY, A COR- PORATION OF GERMANY.

METHOD OF REGENERATING PLATINUM CONTACT SUBSTANCES.

SPECIFICATION forming part of Letters Patent No. 720,361, dated February 10, 1903.

Application filed March 6, 1902. Serial No. 96,922. (No specimens.)

To all whont it may concern:

Be it known that we, OoNsTAN'rIN KRAUSS, Ph.D. ,and RUDOLPH MiiL ER VON BERNECK, chemist, citizens of the Empire of Germany,

residing at Hochst-on-the-Main, Germany,

have invented certain new and useful Improvements in the Method of Restoring the Activity of Platinum Used in Catalytic Processes, of which the following is a specification.

:0 It is known that arsenic has a most deleterious effect on the activity of finely-divided platinum used as a contact substance in the manufacture of sulfuric anhydrid. In other words, it is one of the most powerful of the socalled contact poisons. Although pyritesburner gases may be most carefully purified, yet it happens that traces of arsenic enter the contact-chamber, and thus permanently impair the action of the contact. The arsenic appears to become attached to the platinum, forming fixed compounds with oxygen, which reduce its activity. Hitherto it was necessary to stop Working to remove the contact subtance and to regenerate it in the usual manner by dissolving the platinum in aqua regia and then reduce it again on the contact-carrier, (asbestos or the like.) This manipulation involved great loss by stopping the apparatus, besides the'disagreeable opero ation with aqua regia and the cost of chemicals and Wages. It has been proposed, for instance,by the Aktien-Gesellschaft fiir Zinkindustrie, German Patent No. 115,333, to regenerate the contact substance while work- 5 ing by treating it with chlorin, bromin, or iodin and then distilling the impurities as volatile halogen compounds.

Our present invention relates to the combined application of steam and sulfur dioxid for transforming the fixed compounds of ar- 40 senic into easily-volatile compounds.

If, for instance, steam is introduced into the purified pyrites-burner gases entering the apparatus containing the hot contact, the activity of the latter decreases, but with the mixture of S0 0 S0 and H SO leaving the contact all arsenic gradually escapes, as may easily be proved by examining the condensed acid. Introduction of steam into the .pyrites-burner gases is continued until no further arsenic can be traced in the products. If dried gases are then introduced, the contact regains its activity. The issuing gases now contain increasing quantities of S0 and the normal activity of the platinum contact 5 5 is attained in a short time.

Having now described our invention, what we claim is- The herein-described process of regenerating the platinum contact substance employed I CONSTANTINUKRAUSS. RUDOLPH MULLER VON BERNEOK.

Witnesses ALFRED Bnrsnors, BERNHARD LYDECKER. 

